FSX Verify errors, is there a log file?
I am MZNZCDR working on fsx addon, so I also encountered this problem. Here's how to avoid this error:


intialize the fsx tool.
put friend name anyone then click to GUID button to assign it with ASCII code.
check all model you made that it has a material assigned.
for animation all the animation must be verified after the assigning animation.


After completion of all checks you will find there's no error in export to mdl with animation.x file.

Try these guide lines then call me if it further tease you.